1. Field of the Invention
The present invention relates to a technology that assists generation of machining information for a determination of a necessary tool etc. when a tool path for machining is created in a computer-aided manufacturing (CAM) system from computer-aided design (CAD) workpiece data generated in a CAD system.
The CAD system refers to a computer-based drafting and design support system, and the CAM system refers to an automatic production system or a manufacturing support system based on CAD-generated designs.
2. Description of the Related Art
(1): Conventionally, an operator determines which tool to use to cut a mold etc. Before starting machining, the operator can perform a computer-based verification by creating a tool path for an intended workpiece from the shape characteristics of the tool, cutting conditions, etc. and then by simulating the path. However, to select a different tool based on the verification result to, for example, shorten a machining time even further, the operator must exert their skill or intuition, make a comparison with the past results etc., or make several trial-and-error attempts.
Computers have advanced and become increasingly faster, allowing a reduction of the machining time through a simulation of several trial-and-error attempts, which, however, still require an operator intervention. If a computer is used to make trial-and-error attempts automatically to assist in a tool determination, a database of information about all possessed tools, holders, machines, etc. is constructed and the trial-and-error attempts are made for all tools, thereby determining a combination of tools that offers the shortest machining time. However, a simulation must be performed for all tools, involving a vast quantity of calculations.
(2): During a machining database construction, the shape characteristics etc. of a workpiece, including “outer dimensions,” “volume,” “pocket,” and “hole,” are used as keys. The shape characteristics such as “outer dimensions” and “volume” can be computed with relative ease, but are insufficiently informative as keys for machining characteristics. For the shape characteristics such as “pocket” and “hole” that largely affect machining, it is very difficult to make definitions' from which the shapes are extracted in a computing process.
As a solution to this problem, workpiece categories such as “product name” and “part name” or workpiece shape characteristics such as “pocket” and “hole” are manually added to machining profile data to assist in a computing process. In this case, the computer does not provide a fully automatic machining assistance, and personnel familiar with their own system and machining must construct a machining database.
(3): Explanation of other examples of the conventional technology
Other examples of the conventional technology are disclosed in, for example, patent documents 1 to 5 listed below. The patent documents are found as a result of a document search performed in consideration of relevance to the following topic: “create basic model curves of tool diameter vs. uncut amount for a basic machining profile model, record the curves to a database in advance, select from the database a tool diameter corresponding to a current shape to be machined, perform a cutting simulation, and select a larger- or smaller-diameter tool for use in the next sequence according to where an uncut portion is positioned with respect to a corresponding basic model curve.” The disclosures in the documents are explained below as examples of the conventional technology.
A: Patent Document 1
The document provides an example of an NC data generating method for corner portions by which a process is performed to determine an optimum machining tool for each corner portion based on a calculated uncut amount in the portion, and the process is repeated until all uncut amounts fall within tolerance limits.
B: Patent Document 2
The document provides an example of an NC data generating method for machining uncut portions by which in each machining sequence, tool path data is calculated and a cutting simulation is performed to obtain uncut amount information, which is then transferred to the next cutting sequence for tool path calculation. Thus tool path data is generated in every machining sequence.
C: Patent Document 3
The document provides an example of a machining data generating system in which a tool with the largest diameter that can be inserted into a specified machining area is selected, an uncut amount in the area is calculated, and the calculated information is used to select the next necessary tool from a database.
D: Patent Document 4
The document provides an example of a numerical controller that finds a combination of tools that enables machining in the shortest time, from a tool database that contains entries of tools for which machining times are obtained through machining simulations.
E: Patent Document 5
The document provides an example of a numerical control data generating method by which if a ratio of a machinable area to a selected tool is small, another tool with the next smaller diameter is selected, and if a machining area has a closed shape, a tool with a shape that prevents an uncut portion from being left is selected.
Patent document 1: Japanese Patent Application-Laid-Open No. 2966672 (H06-179150)
Patent document 2: Japanese Patent Application-Laid-Open No. H06-119031
Patent document 3: Japanese Patent Application-Laid-Open No. H06-332515
Patent document 4: Japanese Patent Application-Laid-Open No. H09-50311
Patent document 5: Japanese Patent Application-Laid-Open No. H11-175122
a) According to (1) in the conventional technology, an operator intervention is required. If a computer is used to make trial-and-error attempts automatically to assist in a tool determination, a database of information about all possessed tools, holders, machines, etc. is constructed and the trial-and-error attempts are made for all tools, thereby determining a combination of tools that offers the shortest machining time. However, a simulation must be performed for all tools, involving a vast quantity of calculations.
b) According to (2) in the conventional technology, for the shape characteristics such as “pocket” and “hole” that largely affect machining, it is very difficult to make definitions from which the shapes are extracted in a computing process.
As a solution to this problem, workpiece categories such as “product name” and “part name” or workpiece shape characteristics such as “pocket” and “hole” are manually added to machining profile data to assist in a computing process. In this case, the computer does not provide a fully automatic machining assistance, and personnel familiar with their own system and machining must construct a machining database.
c) According to (3) in the conventional technology, all documents found as a result of the search provide only technological background information or reference information for the present invention. A plurality of known examples is found regarding the following topic: “first perform cutting with a larger-diameter tool, and then select a smaller-diameter tool depending on the status of an uncut portion.” However, there are no hits in a search for documents that provide technological information similar to that in the present invention and cover the following topic: “compare a cutting simulation result with a basic model curve to select a diameter for the next tool.”
The present invention is devised to solve the problems in the conventional technology, with an object of providing absolute evaluation criteria for a given workpiece that do not include shapes or product names. It is another object of the present invention to provide a computer-based assistance easily in a tool selection or a categorization of workpieces by machining characteristics, without having to cause a computer to perform a vast quantity of calculations, when a system is constructed based on the evaluation criteria.